The rapid growth of polymeric membrane processes, ultrafiltration in particular, in water and wastewater treatment sectors in the past several decades has largely been due to its superior reliability as an effective physical barrier against particulate and organic pollutants, disinfection byproduct precursors, and pathogens, compared to the reliability of conventional processes. This advantage holds as long as a membrane's integrity is preserved throughout its lifetime; damage to a membrane is prevalent in full-scale practices (Huisman I H et al., Desalination, 2004, 165:161-164). Membranes are compromised via several mechanisms, including but not limited to, aging of the membrane material, degradation by cleaning chemicals such as chlorine (Causserand et al., Chemical Engineering and Processing: Process Intensification, 2008, 47(1):48-56; Arkhangelsky E et al., Tribol Lett, 2007, 28(2):109-116), physical damage during operation and maintenance (e.g., air or water hammer) (Gijsbertsen-Abrahamse A J et al., Desalination, 2006, 194(1-3):251-258), damage by objects that are not removed by pretreatment (Guo H et al., Water Res, 2010, 44(1):41-57), fracturing due to high transmembrane pressure (Gijsbertsen-Abrahamse A J et al., Desalination, 2006, 194(1-3):251-258; Oxtoby S et al., Water Supply, 2003, 3(5-6):1-7), and breakage of hollow fibers. A compromised membrane results in the deterioration of product water quality and, if significant, system failure.
Unfortunately, there is a lack of technology that can properly address this problem; existing techniques focus mostly on detecting whether the membrane and its associated components such as module sealing have defects (Guo H et al., Water Res, 2010, 44(1):41-57; Krantz W B et al., Desalination, 2011, 283:117-122). Indirect techniques such as particle counting and turbidity monitoring assess the integrity during operation, but they are not preferred because of the low sensitivity (Walsh M E et al., J Water Supply: Res Technol-AQUA, 2005, 54(2):105-114; Cleveland D J et al., J MembrSci, 2008, 318(1-2):176-181). Pressure decay tests (PDTs) and diffusive air flow (DAF) tests are the most commonly used direct techniques because of their simplicity, reproducibility, and high sensitivity of damage detection (Guo H et al., Water Res, 2010, 44(1):41-57; Johnson W T, Desalination, 1997, 113(2-3):303-307; Johnson W T, Filtr Sep, 1998, 35(1):26-29; Bennett A, Filtr Sep, 2005, 41(1):30-33). When a failure in a membrane is suspected, however, the precise location of the damage must be identified before it can be repaired or replaced (Oxtoby S et al., Water Supply, 2003, 3(5-6):1-7). For example, damaged hollow fiber membranes can be isolated by manually sealing the fiber's open ends, although, in most cases, fiber failure requires replacement of the entire membrane module because it is difficult to locate broken fibers (Membrane filtration guidance manual; Office of Ground Water and Drinking Water, EPA: Cincinnati, Ohio, 2005). Repairing or replacing membranes requires equipment disassembly and significant loss of process run time.
There is a need for a method of repairing a damaged polymeric membrane without requiring the knowledge of damage location or the disassembly of a system. The present invention meets this need.